Abstract: Electrolytic water was used to improve the ultrafine grinding effect of raw gypsum with colloid mill, FTIR and other methods were employed to characterize the solution and ultrafine grinding products. The results showed that the electrolysis-modified water had a significant positive effect on the ultrafine grinding of raw gypsum. Under the conditions of raw gypsum slurry concentration of 16% and ultrafine grinding time of 25 min, the d₉₀ of ultrafine grinding product was reduced from 54.6 μm to 2.21 μm, while the specific surface area was promoted from 203 cm²/g to 2265 cm²/g with water modification time of 20 min. When the water was treated by electrolysis for 20 min, the total content of hydrophilic hydroxyl groups of water increased by 2.42 percentage points, which enhanced the affinity between water and active point on raw gypsum surface, resulting in a decrease in the viscosity of raw gypsum slurry by 16.74 mPa·s. The above effects can improve the fluidity of raw gypsum slurry and enhance the shearing effect of colloid mill gear on raw gypsum, which increased the internal cracks of the raw gypsum, the penetration of the modified water into the raw gypsum, and the plane spacing, microscopic strain, dislocation density of the gypsum increased, while the crystallinity and grain size became smaller, and finally the efficiency of raw gypsum superfine grinding was improved.